Celebs in the Stands at Wimbledon

The trove of cards, issued in 1910, includes ones of Ty Cobb, Honus Wagner and Cy Young, and few collections have ever been found in such good condition.

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"It's like finding the Mona Lisa in the attic,” Kissner said.

The Wagner card could be of particular interest — and is particularly rare. That is because his baseball cards were included in American Tobacco Co.'s packs of cigarettes, and Wagner's cards were pulled from the company's card circulation, reportedly because he didn't want to encourage smoking.

After Kissner found the box of cards, he carefully put it on the dresser and went back to digging in the attic. About two weeks later, he and his family learned they may have just inherited one of the most exciting finds in sports history.

After the cards were authenticated, the cards will go up to auction by Heritage Auctions, which expects to sell all the cards in the next three years, the AP reported.